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Custom firmware often allow homebrew applications or ROM image backups to run directly within the game console, unlike official firmware, which usually only allow signed or retailed copies of software to run. Because custom firmware is often associated with software piracy, console manufacturers such as Nintendo and Sony have put significant effort into blocking custom firmware and other third party devices and content from their game consoles.

Custom firmware is commonly seen in the PlayStation Portable handhelds released by Sony. Notable custom firmware include M33 by Dark_AleX as well as those made by others such as the 5.50GEN series, Minimum Edition (ME/LME), and PRO.

Custom firmware is also seen in the PlayStation 3 console. Only early "Fat" and Slim (CECH-20xx until CECH-25xx) model to run custom firmware. Slim (CECH-30xx) and Super Slim model can only run HEN (Homebrew Enabler), which has functionality similar to a custom firmware.

The PlayStation Vita, has eCFW meaning custom firmware for PSP running in the PSP emulator of the PS Vita. These eCFWs include ARK, TN-V and more recently, Adrenaline, which includes more features since it was hacked from the native side. In 2016 things changed for the PS Vita scene, as a Team called Molecule released HENkaku which alters the OFW of the PS Vita on firmware 3.60 and by doing so creating a custom firmware on your handheld, opening it up like never before. The team behind the original HENkaku has also released taiHEN. taiHEN is a framework on which the newest version of HENkaku runs. It is a way to load plugins at the system level like you were used to on the PSP allowing you to change/add function to your console.[1] Enso is a bootloader vulnerability of the Vita that make HENkaku permanent and allows to run itself on the boot. So the Vita has a full CFW with HENkaku taiHEN and Enso. People on 3.60 can also update to 3.65 without losing HENkaku Enso.

The modding scene of the Nintendo 3DS involves both flash cartridges which emulate an original game cart (which can be solely used to play untouched game cart ROM backups) and custom firmware (software which patches the official firmware "on the fly"), which requires an exploit to obtain control of the ARM9, the 3DS' security coprocessor. The current most widely used CFW is Luma3DS, developed by Aurora Wright and TuxSH, which allows unsigned CIA (CTR Importable Archives) files to be installed on the Nintendo 3DS devices, provides region-free features, exception handling for homebrew software developers etc.. Other past and abandoned CFWs included Gateway (a proprietary CFW locked to a flash cartridge via DRM and the first publicly available one), Pasta, RxTools (the first free and widely used one),Cakes CFW[2] (the first open source CFW, which used a modularized approach for patches and was the inspiration for the following ones), ReiNAND, which Luma3DS was originally based on, and Corbenik;[3] as of now the only custom firmware still currently being developed is Luma3DS (previously known as AuReiNAND). 3DS CFWs used to rely on "EmuNAND"/"RedNAND", a feature that boots the system from an unpartitioned space of the SD card containing a copy of the 3DS' NAND memory. These EmuNANDs could protect the 3DS system from bricking, as the usual system NAND was unaffected if the emuNAND is no longer functioned properly or was otherwise unusable. EmuNANDs could also be updated separately from the usual system NAND, allowing users to have the latest system version on the EmuNAND while retaining the vulnerable version on the system NAND; thus making online play and Nintendo eShop access possible on outdated 3DS system versions.
EmuNANDs were obsoleted by the release of arm9loaderhax, a boot-time ARM9 exploit that allowed people to safely use SysNAND and update it, as CFWs started patching the OS' update code so that official updates wouldn't remove the exploit. However, this exploit required a downgrade to a very early system version to get the console's unique OTP, necessary for the installation.
On May 19, 2017 a new exploit basis called sighax was released, replacing arm9loaderhax and allowing users to get even earlier control of the system, granting code execution in the context of the bootROM and thus a cleaner environment, with no downgrades or OTP required. Boot9Strap, a user-friendly version of sighax, was released.
At the same time, another bootROM exploit called ntrboot was announced, which allows people to use a backdoor present in the bootROM to get full system control on any 3DS console regardless of the firmware version (as the bootROM can't be updated), only requiring a modified DS flash cartridge and a magnet. The initial release was on August 12, supporting the AceKard 2i and R4i Gold 3DS RTS cartridges.

The practice of replacing the default Android operating system of a device, present in read-only memory (ROM), with a modified version of the OS or a completely different OS is called "ROM flashing". The procedure is generally not supported by device manufacturers, and requires advanced knowledge of OS mechanics. However, recent years have brought many more manufacturers, such as LG,[4] Motorola,[5] OnePlus,[6] Google[7] (but not on devices sold by Verizon), and Sony[8] allowing customers to unlock the bootloader, bypassing secure boot, without the need for exploits. The "custom ROMs" being used may include different features, require less power, or offer other benefits to the user.